Speed control system of fan motor of air conditioner

ABSTRACT

A speed control system of a fan motor of an air conditioner is disclosed. A speed control system of a fan motor of an air conditioner comprises: an inverter having a power output terminal connected to a single-phase power input terminal of the fan motor which has a single-phase stator including a main coil and a sub coil, an induction rotor and a permanent magnet rotor installed between the stator and the induction rotor; and a three-phase driving motor connected to the power output terminal of the inverter and driving a compressor of an air conditioner by power received from the inverter.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a fan motor of an air conditioner, andparticularly, to a speed control system of a fan motor of an airconditioner.

2. Description of the Background Art

In general, a single-phase induction motor is used as a fan motor of anair conditioner. To generate a rotating torque, the signal-phaseinduction motor supplies both a magnetizing current generating arotating magnetic field and an induced current generated in a rotor towindings connected to an external power terminal.

The single-phase induction motor has limit in improving efficiency by aprimary copper loss and a secondary copper loss of a rotor. To solvesuch limit, an HIM (Hybrid Induction Motor) shown in FIGS. 1 and 2 isbeing used recently as a fan motor of the air conditioner. Hereinafter,an induction motor having a permanent magnet rotor is defined as an HIM.

FIG. 1 is a schematic sectional view of the HIM in accordance with theconventional art.

FIG. 2 is a schematic top view taken along line B-B′ of the HIM of FIG.1.

As shown in FIGS. 1 and 2, a stator 102 is installed inside a bracket101 of the HIM in accordance with the conventional art, and an inductionrotor 103 is installed inside the stator 102. A plurality of slots 105are protrudingly formed inside the stator 102, and coils 106 arerespectively wound on the slots 105.

Aluminum rotor bars 107 are vertically inserted in a plurality of airgaps 103A formed at an edge of the rotor 103 in a vertical direction,and the aluminum rotor bars 107 are connected to each other by an endring 108.

A rotating shaft 109 for transferring a rotary force of the rotor 103 tothe outside is installed at an air gap 103B formed at the center of theinduction rotor 103. The rotating shaft 109 becomes rotatable by anoilless bearing 110 installed at the bracket 101.

A permanent magnet rotor 104 for rotating the rotor 103 at a strongmagnetic flux while being rotated by a rotating magnetic field generatedfrom the stator 102 is installed between the stator 102 and theinduction rotor 103.

When an AC voltage is applied to the HIM in accordance with theconventional art, the permanent magnet rotor 104 is rotated by a currentapplied to the coil 106 of the stator 102, and the rotated permanentmagnet rotor 104 generates a rotating magnetic field having a strongmagnetic flux, thereby rotating the induction rotor 103. At this time,the low inertial permanent magnetic rotor 104 separated from a fan (notshown) is rotated by the rotating magnetic field of the stator 102, anda torque generating magnetic flux is supplied to the induction rotor 103by the rotating magnetic field of the permanent magnet rotor 104, sothat the induction rotor 103 is rotated. Namely, when the permanentmagnet rotor 104 rotated by an oval-shaped rotating field generated fromthe stator of distributing windings is rotated, the permanent magnetrotor 104 generates a rotating magnetic field having a strong magneticflux, thereby rotating the induction rotor 103. Therefore, the HIM isoperated at high efficiency, making a low noise.

Speed characteristics of the HIM and a general induction motor inaccordance with the conventional art will now be described withreference to FIG. 3.

FIG. 3 is a graph showing a speed characteristic of the HIM and thegeneral induction motor according to the conventional art.

As shown, when a speed control system of controlling a rotating speed ofa fan motor by controlling a voltage applied to the fan motor (HIM) isapplied to the HIM, a speed control range is restricted according to thevoltage (e.g., 790˜880 rpm (revolution per minute)). Namely, because ofthe permanent magnet rotor 104, the speed control range is restrictedwithin 790˜880 rpm. For this reason, the speed control system inaccordance with the conventional art cannot be applied to the airconditioner requiring a speed control range of 100 rpm or more.

Meanwhile, an induction motor used as a fan motor of an air conditionerin accordance with the conventional art is disclosed in U.S. Pat. No.6,819,026 registered on Nov. 16^(th) in 2004.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide a speedcontrol system of a fan motor of an air conditioner capable of extendinga speed control range of a fan motor by controlling a fan motor usingoutput power of an inverter for driving a driving motor of a compressor.

Another object of the present invention is to provide a speed controlsystem of a fan motor of an air conditioner capable of extending a speedcontrol range of a fan motor without any special additional cost bycontrolling a fan motor using a frequency of output power of an inverterfor driving a driving motor of a compressor without a special device.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described herein,there is provided a speed control system of a fan motor of an airconditioner comprising: an inverter having a power output terminalconnected to a single-phase power input terminal of the fan motor whichhas a single-phase stator including a main coil and a sub coil, aninduction rotor and a permanent magnet rotor installed between thestator and the induction rotor; and a three-phase driving motorconnected to the power output terminal of the inverter and driving acompressor of an air conditioner by power received from the inverter.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described herein,there is provided a speed control system of a fan motor of an airconditioner comprising: an inverter having a power output terminalconnected to a three-phase power input terminal of a fan motor which hasa three-phase stator including a three-phase balancing coil, a inductionrotor and a permanent magnet rotor installed between the stator and theinduction rotor; and a three-phase driving motor connected to the poweroutput terminal of the inverter and driving a compressor of an airconditioner by power received from the inverter.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute aunit of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

In the drawings:

FIG. 1 is a schematic sectional view of an HIM in accordance with theconventional art;

FIG. 2 is a schematic top view taken along line B-B′ of the HIM of FIG.1;

FIG. 3 is a graph showing a speed characteristic of the HIM and ageneral induction motor in accordance with the conventional art;

FIG. 4 is a circuit view showing a structure of a speed control systemof a fan motor of the air conditioner in accordance with an embodimentof the present invention;

FIG. 5 is a circuit view showing a structure of a speed control systemof a fan motor of an air conditioner in accordance with anotherembodiment of the present invention; and

FIG. 6 is a table showing a correlation between a speed of a fan motorof the air conditioner and a power frequency according to the number ofpoles of a three-phase driving motor and the number of poles of a fanmotor in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings.

Hereinafter, preferred embodiments of a speed control system of a fanmotor of an air conditioner in accordance with the present inventioncapable of extending a speed control range of a fan motor by controllinga fan motor using output power of an inverter for driving a drivingmotor of a compressor, and of extending a speed control range of a fanmotor without any special additional cost by controlling a fan motorusing a frequency of output power of the inverter for driving a drivingmotor of a compressor without a special device, will now be describedwith reference to FIGS. 4 to 6.

FIG. 4 is a circuit view showing a structure of a speed control systemof a fan motor of an air conditioner in accordance with one embodimentof the present invention.

As shown, the speed control system of the fan motor of the airconditioner in accordance with the present invention includes: aninverter 42 having a power output terminal connected to a single-phasepower input terminal of the fan motor 41 which has a single-phase stator102 including a main coil and a sub coil, an induction rotor 103 and apermanent magnet rotor 104 installed between the stator and theinduction rotor; and a three-phase driving motor 43 connected to thepower output terminal of the inverter 42 and driving the compressor ofthe air conditioner by power received from the inverter 42. Here, thethree-phase driving motor 43 is a three-phase brushless direct current(BLDC) motor, a three-phase induction motor or a three-phase HIM (HybridInduction Motor).

A control means (not shown) outputs a control signal for varying acompression capacity of the compressor to the inverter 42 according toan indoor temperature and a desired temperature of a user.

The inverter 42 varies a frequency of driving power of the three-phasedriving motor 43 as a switching device of the inverter 42 is switchedaccording to the outputted control signal. The rotating speed of thethree-phase driving motor 43 is varied according to the varied frequencyof the driving power. At this time, the fan motor 41 receives the variedfrequency of the driving power from the inverter 42, therebyinterworking with the three-phase driving motor 43 of the compressor andthus rotating.

However, in general, the three-phase driving motor 43 rotates at aspecific rpm (e.g., 2400 rpm) by the frequency of the driving poweroutputted from the inverter 42, and the fan motor 41 should rotate at anrpm (e.g., 800 rpm) of about ⅓ of the specific rpm. For example, thethree-phase driving motor 43 rotates at 1200 rpm˜3600 rpm by 60 Hz, afrequency of the driving power outputted from the inverter 42, and, thefan motor 41 should rotate at 400 rpm˜1200 rpm. Accordingly, a processfor allowing a ratio of the number of rotation of the three-phasedriving motor 43 to the number of rotation of the fan motor 41 to be 3:1by the frequency of the driving power is required. To this end, thepresent invention is designed so that the number of poles of the fanmotor 41 is three times greater than the number of poles of thethree-phase driving motor 43 of the compressor.

And, because the fan motor 41 is a single-phase HIM having a statorincluding a main coil and a sub coil, the fan motor 41 receivessingle-phase power from a three-phase power output terminal of thethree-phase inverter 42.

Another embodiment of a speed control system of a fan motor of an airconditioner in accordance with the present invention will now bedescribed with reference to FIG. 5.

FIG. 5 is a circuit view showing a structure of a speed control systemof the fan motor of the air conditioner in accordance with anotherembodiment of the present invention.

As shown, the speed control system of the fan motor of the airconditioner in accordance with another embodiment of the presentinvention includes: an inverter 52 having a power output terminalconnected to a three-phase power input terminal of a fan motor 51 whichhas a three-phase stator including a three-phase balancing coil, aninduction rotor and a permanent magnet rotor installed between thestator and the induction rotor; and a three-phase driving motor 53connected to a power output terminal of the inverter 52 and driving acompressor of the air conditioner by power received from the inverter52. Here, the three-phase driving motor 53 is a three-phase BLDC(Brushless Direct Current) motor, a three-phase induction motor or athree-phase HIM (Hybrid Induction Motor).

In the speed control system of the fan motor of the air conditioner inaccordance with another embodiment of the present invention having sucha structure, preferably, a three-phase HIM having a three-phase statorincluding a three-phase balancing coil is used as the fan motor 51instead of a single-phase HIM having a stator including a main coil anda sub coil. Accordingly, the speed control system of the fan motor ofthe air conditioner in accordance with another embodiment of the presentinvention has no difference from the speed control system of the fanmotor of the air conditioner in accordance with one embodiment of thepresent invention except that the fan motor 51 is connected to athree-phase power output terminal of the three-phase inverter 52 andreceives the driving power.

A specific example according to the present invention will now bedescribed with reference to FIG. 6.

FIG. 6 is a table showing a correlation between a speed of a fan motorof an air conditioner and a power frequency according to the number ofpoles of a three-phase driving motor and the number of poles of the fanmotor in accordance with the present invention.

Referring to embodiment 1 of FIG. 6, the number of poles of thethree-phase driving motor and the number of poles of the fan motor aresix and eighteen, respectively, and therefore have a correlation ratioof 1:3. The three-phase driving motor rotates at 4200˜600 rpm accordingto the output power frequency (210˜30 Hz) of the inverter, and the fanmotor can rotate at 1400˜200 rpm.

Referring to embodiment 2 of FIG. 6, the number of poles of thethree-phase driving motor and the number of poles of the fan motor arefour and twelve, respectively, and thus have a correlation ratio of 1:3.The three-phase driving motor rotates at 6300˜900 rpm according to theoutput power frequency (210˜30 Hz) of the inverter and the fan motor canrotate at 2100˜300 rpm.

Referring to embodiment 3 of FIG. 6, the number of poles of thethree-phase driving motor and the number of poles of the fan motor aretwo and six, respectively, and thus have a correlation ratio of 1:3. Thethree-phase driving motor rotates at 12600˜1800 rpm according to theoutput power frequency (210˜30 Hz) of the inverter and the fan motor canrotate at 4200˜600 rpm.

As described in embodiments 1 to 3 of FIG. 6, the present invention canremarkably extend the speed control range of the fan motor of the airconditioner compared to the conventional art.

As so far described, the speed control system of the fan motor of theair conditioner according to the present invention can extend a speedcontrol range of a fan motor by controlling the fan motor using outputpower of the inverter that drives a driving motor of a compressor.

Also, the speed control system of the fan motor of the air conditioneraccording to the present invention can extend a speed control range ofthe fan motor without any special additional cost by controlling the fanmotor using a frequency of the output power of the inverter that drivesa driving motor of a compressor without a special device.

As the present invention may be embodied in several forms withoutdeparting from the spirit or essential characteristics thereof, itshould also be understood that the above-described embodiments are notlimited by any of the details of the foregoing description, unlessotherwise specified, but rather should be construed broadly within itsspirit and scope as defined in the appended claims, and therefore allchanges and modifications that fall within the metes and bounds of theclaims, or equivalence of such metes and bounds are therefore intendedto be embraced by the appended claims.

1. A speed control system of a fan motor of an air conditionercomprising: an inverter having a power output terminal connected to asingle-phase power input terminal of the fan motor which has asingle-phase stator including a main coil and a sub coil, an inductionrotor and a permanent magnet rotor installed between the stator and theinduction rotor; and a three-phase driving motor connected to the poweroutput terminal of the inverter and driving a compressor of an airconditioner by power received from the inverter.
 2. The system of claim1, wherein the fan motor receives single-phase power from the poweroutput terminal of the inverter that supplies three-phase power to thethree-phase driving motor.
 3. The system of claim 1, wherein the numberof poles of the fan motor is three times greater than the number ofpoles of the three-phase driving motor that drives the compressor. 4.The system of claim 1, wherein the number of poles of the three-phasedriving motor of the compressor and the number of poles of the fan motorare six and eighteen, four and twelve, and two and six, respectively. 5.The system of claim 1, wherein the three-phase driving motor is athree-phase brushless direct current (BLDC) motor.
 6. The system ofclaim 1, wherein the three-phase driving motor is a three-phaseinduction motor.
 7. The system of claim 1, wherein the three-phasedriving motor is a three-phase hybrid induction motor (HIM).
 8. Thesystem of claim 1, further comprising: a control means for outputting acontrol signal for controlling the inverter in order to vary acompression capacity of the compressor according to an indoortemperature and a desired temperature of a user.
 9. A speed controlsystem of a fan motor of an air conditioner comprising: an inverterhaving a power output terminal connected to a three-phase power inputterminal of a fan motor which has a three-phase stator including athree-phase balancing coil, a induction rotor and a permanent magnetrotor installed between the stator and the induction rotor; and athree-phase driving motor connected to the power output terminal of theinverter and driving a compressor of an air conditioner by powerreceived from the inverter.
 10. The system of claim 9, wherein the fanmotor receives three-phase power from the power output terminal of theinverter that supplies three-phase power to the three-phase drivingmotor.
 11. The system of claim 9, wherein the number of poles of the fanmotor is three times greater than the number of poles of the three-phasedriving motor that drives the compressor.
 12. The system of claim 9,wherein the number of poles of the three-phase driving motor of thecompressor and the number of poles of the fan motor are six andeighteen, four and twelve, and two and six, respectively.
 13. The systemof claim 9, wherein the three-phase driving motor is a three-phase BLDCmotor.
 14. The system of claim 9, wherein the three-phase driving motoris a three-phase induction motor.
 15. The system of claim 9, wherein thethree-phase driving motor is a three-phase HIM (hybrid induction motor).16. The system of claim 9, further comprising: a control means foroutputting a control signal for controlling the inverter in order tovary a compression capacity of the compressor according to an indoortemperature and a desired temperature of a user.